Solar thermochemical reactions Ⅱ： Synthesis of 2-aminothiophenes via Gewald reaction induced by solar thermal energy

Green conditions have been developed for the synthesis of substituted 2-aminothiophenes employing multicomponent reactions of a ketone with active methylene nitrile and elemental sulphur induced by free solar thermal energy.     

On convergence of numerical schemes for hyperbolic conservation laws with stiff source terms

We deal in this study with the convergence of a class of numerical schemes for scalar conservation laws including stiff source terms. We suppose that the source term is dissipative but it is not necessarily a Lipschitzian function. The convergence of the approximate solution towards the entropy solution is established for first and second order accurate MUSCL and for splitting semi-implicit methods.

     

Courants-Traces

Sans résumé

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Received: 20 August 1995 / Revised version: 20 April 1996     

OSCILLATION THEORY TO SOME COMPLEX LINEAR LARGE DIFFERENTIAL EQUATIONS

In this paper, some complex linear differential equations are investigated. Many results on the relation between solutions and their derivatives are obtained.     

Water-Soluble O-, S- and Se-Functionalized Cyclic Acetyl-triaza-phosphines. Synthesis,Characterization and Application in Catalytic Azide-alkyne Cycloaddition

The 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane (DAPTA) derivatives, viz. the already reported 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane 5-oxide (DAPTA=O, 1), the novel 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane-5-sulfide (DAPTA=S, 2), and 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane-5-selenide (DAPTA=Se, 3), have been synthesized under mild conditions. They are soluble in water and most common organic solvents and have been characterized using ¹H and ³¹P NMR spectroscopy and, for 2 and 3, also by single crystal X-ray diffraction. The effect of O, S, or Se at the phosphorus atom on the structural features of the compounds has been investigated, also through the analyses of Hirshfeld surfaces. The presence of 1–3 enhances the activity of copper for the catalytic azide-alkyne cycloaddition reaction in an aqueous medium. The combination of cheaply available copper (II) acetate and compound 1 has been used as a catalyst for the one-pot and 1,4-regioselective procedure to obtain 1,2,3-triazoles with high yields and according to ‘click rules’.     

Synthesis,characterization and cytotoxic activity of ferrocenyl hydrazone complexes containing a furan moiety

A ferrocenyl ligand 1 was prepared from condensation of 5-methyl-2-furaldehyde with l,l′-diacetylferrocene dihydrazone. This ligand forms 1:1 complexes with cobalt(II), nickel(II), copper(II) and zinc(II) 2–5 in good yield. Characterization of the ligand and complexes was carried out using infrared, nuclear magnetic resonance, mass spectra, electronic absorption, magnetic susceptibility, molar conductivity, and elemental analysis. Cytotoxic activity of the prepared ligand and its complexes were tested against different human cancer cell lines. The results suggested that the synthesized compounds were more potent than the comparative standards drugs used in most cases, whereas they had less activity in the others.     

Langmuir-Blodgett films as aligning layers for homeotropic alignment of liquid crystal molecules

The first single crystal structure of a Group VA halide salt with three equivalent long n-alkyl chains, benzyltrioctadecylammonium bromide (BzN18Br), is reported. It consists of alternating interdigitated and non-interdigitated regions of alkyl chains separated by ionic planes. Two chains per molecule are paired and extend to one side in a non-interdigitated region. The third chain is on the opposite side of the ionic plane and pairs intermolecularly to form an adjacent, interdigitated region. The thickness of two nearly extended molecules defines the bilayer unit-two ionic planes flanked by a region with intramolecularly paired chains and separated by an interdigitated chain region. Powder X-ray diffraction and optical microscopy data of liquid crystalline BzN18Br are consistent with an enantiotropic smectic A₂ (SmA₂) phase: the three n-alkyl chains of each molecule are projected from one side of an ionic plane, and head groups of neighbouring molecules are oriented head-to-head, in a non-interdigitated bilayer assembly. The structure of BzN18Br fills an important gap in our knowledge about the crystal packing of ammonium and phosphonium salts with one-four equivalent long n-alkyl chains. A comparison of their packing arrangements is made and the transitional nature of the BzN18Br structures is demonstrated. Although salts with one, two, or three long n-alkyl chains form SmA₂ phases, each is distinctive in its molecular packing. A large molecular reorganization accompanies the crystal-to-liquid crystal transition of BzN18Br.     

A theoretical analysis of a new finite volume scheme for second order hyperbolic equations on general nonconforming multidimensional spatial meshes

We consider the wave equation, on a multidimensional spatial domain. The discretization of the spatial domain is performed using a general class of nonconforming meshes which has been recently studied for stationary anisotropic heterogeneous diffusion problems, see Eymard et al. (IMAJ Numer Anal 30 (2010), 1009–1043). The discretization in time is performed using a uniform mesh. We derive a new implicit finite volume scheme approximating the wave equation and we prove error estimates of the finite volume approximate solution in several norms which allow us to derive error estimates for the approximations of the exact solution and its first derivatives. We prove in particular, when the discrete flux is calculated using a stabilized discrete gradient, the convergence order is begin{align*} h_mathcal{D}end{align*} (resp. k) is the mesh size of the spatial (resp. time) discretization. This estimate is valid under the regularity assumption begin{align*}uin C^3(lbrack 0,Trbrack;C^2(overline{Omega}))end{align*} for the exact solution u. The proof of these error estimates is based essentially on a comparison between the finite volume approximate solution and an auxiliary finite volume approximation. © 2012 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2013     

Green magnetic snail shell hydroxyapatite sorbent for reliable solid-phase extraction of pesticides from water samples

To address sustainability issues, the green synthesis of nanomaterials has recently received considerable attention. This article addresses a novel and cost-effective adsorbent for the extraction of eight phenyl-N-methylcarbamate insecticides from water samples. We first synthesized a magnetite/hydroxyapatite nanocomposite using snail shell powder via an environmental friendly approach. The morphology and physicochemical properties of magnetic hydroxyapatite were characterized by Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and scanning electron microscopy. Magnetic extraction parameters were optimized using a Doehlert matrix. Under optimum conditions, the magnetic extraction coupled with a LC–MS method shows good linearity with R² ≥ 0.9982, suitable intra- and interday precision, and limits of detection and quantification in the range of 0.052–0.093 μg/L and 0.11–0.31 μg/L, respectively. Satisfactory relative recoveries of all carbamates were achieved from fortified water samples in the range of 93.89–101.01%.